JPS6036680A - Method for carrying out electric protection of buried pipeline - Google Patents

Abstract

PURPOSE:To carry out effectively the electric protection of a buried pipeline by placing curved magnesium galvanic electrodes connected with a conductor around the pipe of the pipeline at almost equal intervals so as to form and electric circuit. CONSTITUTION:Two curved magnesium galvanic electrodes 27 connected in series with a conductor 25 coated with an insulator so as to enclose a pipe 1 buried in the ground are connected to a sheathed cable conductor 9. Each terminal 5 for taking electric current out of the pipe 1 is connected to a sheathed cable conductor 7. The conductors 7, 9 are introduced into a terminal box 13 placed on the surface of the ground through a capable pipe 11. The terminals of the conductors 7, 9 are electrically connected to produce anticorrosive action.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electrolytically protecting a pipeline buried in soil using a magnesium galvanic anode.

Cathodic protection is a method of protecting pipelines buried in soil from corrosion. The galvanic anodic corrosion protection method, which is one of the cathodic protection methods, uses I! A method for creating an anti-corrosion environment that protects pipelines from corrosion through battery action, which is formed by burying gas-chemically base materials, such as magnesium, at a distance and connecting the pipe and the magnesium material with an insulated conductor. It is.

By the way, in order to prevent corrosion of pipeline pipes using the conventional magnesium galvanic anodic corrosion protection method, as shown in Fig. 500-2000
Coated electrodes 3 made of magnesium galvanic anodes coated with a material to be described later are spaced apart from each other and embedded at regular intervals along the length of the pipe 1. Covered electrode 3
A sheathed cable conductor 9 is connected to the sheathed cable conductor 9. A sheathed cable conductor 7 is connected to the current extraction terminal 5 of the pipe 1,
The sheathed cable conductors 7 and 9 are guided through a conduit 11 into a terminal box 13 installed on the ground surface, and their ends are electrically connected. The coating 11 pole 3 is a W rod-shaped magnesium galvanic anode 1 as shown in the partially broken cross-sectional view of FIG.
9 is covered with a chemical called backfill 15 made of bentonite, gypsum, porcelain, etc. and housed in a cloth bag 21, and the conductor 17 from one end of the current anode 19 is guided outside the cloth bag 21! #Be done. The coated electrode 3 usually has a length of about 1000 m and a diameter of about 20011 m.

According to the conventional galvanic anodic corrosion protection method, as shown in FIG. In cases where the resistivity, coating resistance, etc. on the pipe's outer surface are extremely large, and in environments where corrosiveness varies greatly due to differences in soil properties in the circumferential direction of the pipe's outer surface, uniformity and The disadvantage is that sufficient corrosion protection cannot be achieved. Furthermore, it has been said that the higher the soil resistivity, the lower the corrosiveness of the soil, but this is not necessarily true.As shown in Figure 3, even in an environment with high soil resistivity, it can be subject to significant corrosion. Yes (3rd
The figure is Iwao Matsushima: Tomb 11 of 19 volumes of high-pressure gas (1982P55)
7) Cathodic protection that can uniformly and sufficiently protect the entire outer surface of a pipe even in soil environments that are highly corrosive and where the effectiveness of conventional galvanic anodic protection methods is expected to decrease. There is a strong need for a method.

An object of the present invention is to provide a method for cathodic protection using a magnesium galvanic anode, which eliminates and improves the above-mentioned drawbacks regarding the cathodic protection of buried pipeline pipes, and which meets the demands. The above objectives can be achieved by providing a method as described in the scope.

That is, the present invention provides a method for cathodic protection of a buried pipeline using a magnesium galvanic anode connected to the pipe through a conductor so as to form a circuit with the pipe of the pipeline buried in the soil. A method for cathodic protection of a buried pipeline characterized by using a curved magnesium galvanic anode connected to the pipe via a conductor so as to be spaced approximately equidistant from the pipe and to form an electric circuit with the pipe. It is something.

Next, the present invention will be explained in detail.

The present inventors conducted a detailed investigation into the corrosion status of many pipelines buried in various soils that had been treated with a stain corrosion prevention method using the magnesium galvanic anode method. It was found that there is a difference in the effect, and furthermore, this phenomenon is explained by the fact that at the circumference of the pipe in which one cell action is formed, one flow Ltb-anode flows from one point on the circumference to each point on the circumference. It is assumed that this is due to the non-uniformity of the current density flowing into the surface of each point due to the non-uniform distance.

As a measure to suppress the above phenomenon, it is recommended that the distance from the C magnesium galvanic anode to each point on the circumference of the pipe outer surface be uniform in the circumferential direction of the pipe where one battery action is formed. As a result of consideration, we came up with the idea that by making the magnesium galvanic anode curved and surrounding the pipe so that the distance from the inner surface of the curved anode to the outer surface of the pipe is approximately equal, it is possible to alleviate the non-uniformity of the anti-corrosion effect. did.

In order to further alleviate the above-mentioned non-uniformity, it would be possible to surround the entire circumference of the pipe with a block-shaped galvanic anode instead of the curved anode, but since this would be economically costly, The electrode anode is divided into multiple parts so that the length of the curve is shortened, and the divided anodes are electrically connected in series at approximately equal intervals #1, so that the curved inner surface of each divided anode is approximately equidistant from the outer surface of the pipe. By burying the pipe so that an electric circuit is formed, the entire circle of the pipe (
6) The present invention was completed based on the idea that it is possible to obtain a uniform anticorrosion effect over the circumference.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 4 is a partially broken sectional view of a curved covered electrode used in the method of the present invention. The curved covered electrode 27 has almost the same structure as the covered electrode 3 already explained with reference to FIG. It differs from the coated electrode 3 described in FIG. 2 above only in different points. In order to connect a plurality of curved coated electrodes 27 in series as shown in FIGS.
A curved coated electrode 27 is also used, using a curved magnesium galvanic anode 23 with an insulated coated conductor 25 extending from both ends instead of the conductor 17 extending from one end of the electrode.

FIG. 6 is an explanatory longitudinal cross-sectional view showing a state in which a pipe and a curved covered electrode are buried underground by the method of the present invention.

Two curved covered electrodes 2 connected in series via an insulated covered conductor 25 so as to surround a pipe 1 buried in the soil.
7 is connected to the sheathed cable conductor 9. A sheathed cable conductor 7 is connected to the current extraction terminal 5 of the pipe 1. The cable is guided through a sheathed cable conductor 7 and a nine-wire conduit 11 into a terminal box 13 installed on the ground surface.

A plurality of sets of magnesium galvanic anodes are arranged surrounding the pipe at required intervals in the longitudinal direction of the pipeline. When the respective terminals of the conductors 7 and 9 are electrically connected after the trench has been backfilled, an anticorrosion effect occurs. By disconnecting the electrical connection between the two twisted terminals and measuring the terminal voltage, it is possible to know whether the anticorrosion effect is present or the degree of wear of the galvanic anode 23.

By reinforcing and maintaining the shape of the curved covered electrode 127 by using a non-conductive material, it is possible to maintain an optimal positional relationship with the object to be protected when the curved covered electrode 27 is embedded. It is very suitable as it can maximize the anti-corrosion effect.

Next, the present invention will be explained with reference to examples.

In order to investigate the anticorrosion effect of pipeline pipes to which the method of the present invention is applied, a comparative test of the anticorrosion effect between the method of the present invention and the conventional method was conducted over a period of one year while observing the progress.

The length of the test pipelines is 120 m, the observation points are at the center of the length, and the underground depth is about 200 m (120 m).
It was set to 1N. Both pipes have an outer diameter of 216.3 mtM,
The wall thickness was 7.3 mm, the outer surface was lined with polyethylene of 1.5 mm to 7 mm, and both ends of the pipe were closed.

FIG. 7 is an explanatory longitudinal cross-sectional view showing a state in which a pipe and a curved covered electrode are buried underground by the method of the present invention.

Curved shape with radius of about 10001111 40X 40
X 350 Shape: 200 φ curved magnesium galvanic anode wrapped in backfill and stuffed into a cloth bag
Curved covering 1 of 450! Two of the poles 27 were connected in series by a covered insulated conductor 25, and the curved covered electrode 27 was buried about 1000 meters away from the test pipe 29 in the radial direction so as to constitute a battery operating circuit.

A, B, C, and D shown in the side view of FIG. 8 are points where the potential of the pipe to the ground is measured by the reference electrode.

(9) FIG. 9 is an explanatory longitudinal cross-sectional view showing a state in which a pipe and a corrugated electrode are buried underground by a conventional method. 40
X 40 X 70011+11 straight rod-shaped magnesium flow 'i! A rod-shaped coated electrode 3 consisting of an anode was placed approximately 1000 M away from the test pipe 29 in the radial direction.
The battery was buried to form a circuit for operation. Points a, b, c, and d shown in the side view of FIG. 10 are points where the potential of the pipe to the ground is measured by the reference electrode. The surface area of the magnesium galvanic anode is the same for both methods.

The soil in which the test pipe 29 was buried has a clay layer above the buried pipe and a black soil layer below, and the soil resistivity is 7300 and 13600Ω, respectively, and the soil p
The H values are 6.8 and 5.4, respectively, and the corrosivity of the soil is different in the circumferential direction of the pipe 29.

Table 1 shows A, B, C, D and a of the comparative test.
.

Measured values of the pipe-to-ground potential at measurement points b, c, and d and calculated values from 1 to 1 based on these measured values are shown. The above measured values were based on a saturated calomel electrode.

(10) (l/) According to the method of the present invention, for example, on the 100th day after the start of the test, 7
Lil electric+li td -1010~-990tnV
;Average value is -1000 mV;Dispersion of measured values is 2
0 mV, whereas according to the conventional method, the average value is -9
23 mV; variation Δ is 60 mV. In other words, when comparing the method of the present invention and the conventional method, the average value is 11%.
000mV vs. -623mV, it was found that the corrosion prevention ability of the method of the present invention was better, and the variation △ was 2.
0 mV vs. 6 omV, which shows that the method of the present invention has a more uniform anti-corrosion ability over the circumference of the pipe.

Although the comparison shown is for the 100th day, it can be seen that the method of the present invention is superior to the conventional method in other comparison examples as well.

By the way, observation after 365 days of measurement revealed that there were no adverse effects on the coating film, such as over-corrosion protection or cathodic peeling of the polyethylene lining film.

Therefore, according to the method of the present invention, a uniform anticorrosion current flows into each point on the circumference of the pipe, and it can be seen that the pipe is in a favorable state.

(/ko) As mentioned above, the method of the present invention can be used to prevent corrosion of pipelines even in adverse environments where the soil resistivity and soil corrosivity are high, and the corrosivity of the soil is significantly different around the outer circumference of the pipe. By maintaining a uniform anti-corrosion potential in the circumferential direction of the pipe's outer surface and providing a strong anti-corrosion potential over the entire pipe, it is extremely effective in preventing corrosion of pipeline pipes.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional explanatory diagram showing a state in which a pipe and a covered electrode are buried underground in a conventional galvanic anodic corrosion protection method, Fig. 2 is a partially fragmented sectional view of a conventional covered electrode, and Fig. 3 is a diagram showing the relationship between soil resistivity and erosion and pitting depth,
Fig. 4 is a partially broken cross-sectional view of a curved coated electrode used in the method of the present invention, Fig. 5 is a layout diagram of a plurality of curved coated electrodes connected in series, and Fig. 6 is a cross-sectional view of a curved coated electrode used in the method of the present invention. A vertical cross-sectional view showing a pipe and a curved covered electrode buried underground, and FIG. 7 is a vertical cross-sectional view showing a pipe and a curved covered electrode buried underground by the method of the present invention (/3). 8 is a side explanatory view of FIG. 7, and FIG. 9 is a vertical cross-sectional explanatory view showing a state in which the pipe and the covered electrode are buried underground and FL by the conventional method.
FIG. 0 is an explanatory view of the side J1 in FIG. 9. DESCRIPTION OF SYMBOLS 1... Pipe, 3... Covered electrode, 5... Current extraction terminal, 7... Sheathed cable conductor T body, 9...
Sheathed cable conductor, 11... Electric conduit, 13... Terminal box, 15... Back fill, 17...
・Conductor, 1... Magnesium galvanic anode, 21...
Hotei, 23... Curved magnesium galvanic anode, 25...
- Insulated coated conductor, 27... Curved coated electrode, 29...
Pipe for comparison test. Special II' 1 person Representative of Kawasaki Steel Corporation Patent attorney Mura 1) [To Q Tomari (/l)

Claims (1)

[Claims] / In a method for cathodic protection of a buried pipeline using a magnesium galvanic anode connected to the pipe via a conductor to form an electric circuit with the pipe of the pipeline buried in soil, Spaced approximately equidistantly from the line pipe and the pipe! A curved magnesium flow connected to the pipe via a conductor to form an air circuit! A method for cathodic protection of buried pipelines, characterized by using an anode. 2. The method according to claim 1, characterized in that 1 to <Vi2 or more magnesium galvanic anodes are connected in series and arranged to surround a pipe of a pipeline. how to. 3. In the method according to claim 1 or 2, a set of one or more magnesium galvanic anodes is arranged surrounding a pipe of a pipeline. Alternatively, a method characterized by arranging two or more sets at a required interval in the longitudinal direction of the pipeline.